UCC5638FQP

Overview

The UCC5638FQP is a multimode SCSI active terminator designed for seamless integration into Low Voltage Differential (LVD) SCSI Parallel Interface architectures, including SPI-2, SPI-3, and SPI-4. It automatically detects the bus type via the DIFFB pin and switches termination between Single Ended (SE) and LVD modes. The device operates on a TRMPWR supply voltage ranging from 2.7V to 5.25V within an operating temperature range of 0°C to +70°C. In LVD mode, the typical supply current is 25mA, while SE mode draws up to 10mA. The differential impedance is typically 105Ω with a bias voltage of 125mV.

Feature Summary

• Automatically senses the SCSI bus state and dynamically switches between single-ended and low-voltage differential termination modes based on the DIFFSEN signal level.
• Integrates dedicated regulators for 2.7V single-ended and 1.25V/1.3V differential termination, ensuring precise impedance matching and biasing without external components.
• Includes fail-safe biasing and high-impedance shutdown capabilities to maintain signal integrity and protect the bus when HVD devices are detected or the terminator is disconnected.

Applications

• Termination for Ultra2 (SPI-2), Ultra3 (SPI-3), and Ultra320 (SPI-4) SCSI parallel interface buses.
• System design requiring automatic transition from legacy Single Ended SCSI to modern LVD SCSI architectures.
• High-speed data storage controllers and peripheral interfaces utilizing multimode SCSI connectivity.

Procurement Notes

Verify the specific ordering suffix against the manufacturer's latest documentation to confirm package type and reel specifications. Ensure the procurement channel provides valid traceability and RoHS compliance certificates. Confirm that the component status remains active for long-term production requirements before finalizing orders.

Selection Notes

Select this component for applications requiring a monolithic solution for both SE and LVD SCSI termination. Ensure the PCB layout supports the required 120Ω differential impedance standard and manages capacitance balance strictly. Verify that the system power supply can maintain the minimum 2.7V threshold under all load conditions to prevent regulator dropout.

Part Context

This device belongs to the UCC5638 family of multimode SCSI terminators manufactured by Texas Instruments. It serves as a bridge technology allowing systems to support both legacy Single Ended and newer Low Voltage Differential standards within a single integrated circuit architecture.

Replacement Considerations

Public confirmed substitute part numbers: UCC5638FQPTR, UCC5638FQPTR.A.

FAQ

How does the UCC5638 detect and handle High Voltage Differential (HVD) SCSI devices?

When an HVD device is connected, the DIFFSEN line is pulled high above 2.2V. The internal comparators detect this state and switch the terminator to a high-impedance state to prevent interference with the bus.

What is the function of the DIFFB pin in the termination switching process?

The DIFFB pin connects to a noise filter capacitor (typically 4.7µF) that conditions the DIFFSEN signal. This filtering ensures stable detection of the bus mode, preventing false switching due to transient noise during mode transitions.

Why are the HS/GND pins critical for thermal management in this package?

The HS/GND pins are directly connected to the die mount paddle. They conduct heat away from the silicon die to the ground plane on the PCB, reducing junction temperature and improving reliability in the 48-pin LQFP package.